This prospective study from Switzerland included 391 preschool children with with lower airway symptoms. It assessed if the fraction of exhaled nitric oxide (FeNO) is associated with asthma later in their lives, at school age. At follow-up, primary outcome was physician-diagnosed asthma based during school age (166 children completed the study).
FeNO was elevated in the children with later asthma vs. children not developing asthma. Median FeNO was 10.5 vs 7.4 ppb.
Per 5 ppb FeNO increase, the odds ratio for asthma increased by 2.44 without changing when adjusting for confounders. Using the new risk model, children scored at risk had 58% probability for later asthma, whereas the negative predictive value was 78.2%. This risk model is comparable to the classical asthma predictive index (API) but does not require blood sampling. Editor's note: mAPI's major criteria assessment does not require a blood sample - if a skin test is performed.
In this cohort of high-risk preschool children, elevated FeNO is associated with increased risk for school-age asthma.
The current version of mAPI requires 4 wheezing episodes in the past year for a positive test:
Modified Asthma Predictive Index (API) (click to enlarge the image).
Modified Asthma Predictive Index (API) is calculated in children under the age of 3 with ALL of the following:
- 4 wheezing exacerbations in past year
- with one physician-confirmed episode
- plus one major criteria OR 2 minor criteria
Major criteria - one of the following: parental history (mother who had childhood asthma only, father with exercise-induced asthma); physician-diagnosed atopic eczema; allergic sensitization to one aeroallergen.
Minor criteria - two of the following: allergic sensitization to milk, eggs, or peanuts (positive skin or blood test sufficient); wheezing unrelated to respiratory illness (ie, cold);
blood eosinophilia 4% of total white blood cell (WBC) count.
Exhaled nitric oxide in symptomatic children at preschool age predicts later asthma. Singer F, Luchsinger I, Inci D, Knauer N, Latzin P, Wildhaber JH, Moeller A. Allergy. 2013 Apr;68(4):531-8. doi: 10.1111/all.12127. Epub 2013 Feb 18.
Image source: Wikipedia.